Audio system

ABSTRACT

An audio system comprises, according to one aspect of the invention, an audio frequency actuator coupled to a body so as to cause the body to radiate sound when an audio signal is supplied to the actuator by a controller, and an acoustic sensor coupled to said body or to an adjacent body so as to sense acoustic vibrations in said body, the sensor being connected to the controller, whereby the controller is arranged to change the audio signal supplied to the actuator according to the vibrations sensed by the sensor. Another aspect provides an audio system comprising an audio frequency actuator coupled to a body so as to cause the body to radiate sound when an audio signal is supplied to the actuator by a controller, and an acoustic sensor coupled to said body or to an adjacent body so as to sense acoustic vibrations in said body, the sensor being connected to the controller, whereby the controller is arranged to detect predetermined characteristics of the sensed acoustic vibrations and to output an alerting signal in response thereto.

FIELD OF THE INVENTION

This invention relates to an audio system. In one aspect, the inventionrelates to the conversion of an otherwise non-responsive body, forexample a rigid or flexible panel, by the addition of high-force,wide-band acoustic actuators to create a smart surface that can emitand/or receive acoustic signals for the purpose of providing discreetaudio or noise masking, or for sensing attack for security purposes. Theaudio system of this invention can be described as providing a singlesmart surface with Its associated acoustic locus properties or anenclosed volume when a multiplicity of such panels is activated.

The volume to be influenced can be either a singular or multiplearrangements of smart surfaces, fixed or moving.

An additional aspect of this invention also relates to the control ofnoise levels emitted from these smart surfaces or structural elements toavoid environmental noise pollution and create areas (or volumes) ofsound masking or higher levels of noise control from the convertedsurfaces or structural elements.

BACKGROUND OF THE INVENTION

Flat panel loudspeakers are well-known, and typically consist of a rigidpanel of laminated plastics, card or wood with an acoustic transducerattached to one face of the panel. Typical transducers are moving coilelectromagnetic devices or piezoelectric devices.

Similarly traditional cone based directional speakers are well known forreproducing audio signals or masking signals to apparently reduce theeffect of ambient noise.

Magnetostrictive devices are also known, for example of the typedescribed and claimed in our co-pending International Patent ApplicationPCT/GB02/01111. These devices can be used particularly when largerpanels require to be activated to sound. The effect of sounding a largepanel by means of a magnetostrictive actuator is to distribute the soundwaves through the panel, as has been described in our co-pendingapplication, as a distributed planar signal. The effect of sounding alarge panel by means of a magnetostrictive actuator is to distribute thesound waves through the panel, as has been described in our co-pendingapplication, as a distributed planar signal. This type of signal differsfrom directional sound in as much as the distribution of the vibrationsdistribute themselves across the entire extent of the panel or structurereducing the throw but creating a flatter more consistent audio outputacross the entire extent of the driven item.

In a permanent or temporary building, it is known that there aremultiple audio and security systems installed for many differentpurposes; these include audio reproduction, public announcement,supplementary emergency announcement, multi-media, and presentationamplification. Some installations also include active sound maskingsystems or passive sound insulation and privacy screening panels oractive audio systems. Additionally, anti-intruder, counter-espionage orvandalism-detection devices are frequently fitted particularly at low oreasily accessible windows.

Audio reproduction is traditionally achieved using multiple conespeakers or flat panels.

Multi media is normally achieved by installing a dedicated cone speakersystem.

Public announcement is traditionally achieved using multiple conespeakers or flat panels sometimes using the audio reproduction system.

Emergency announcement is traditionally achieved using multiple conespeakers or flat panels sometimes using the audio reproduction system.

Active sound masking is frequently achieved by accurately positioning acone speaker above a personal area, or in the top corners of a roomfocussing down into the centre of the room where people normallycongregate for example around a table. Flat speakers can be used forthis purpose also. In most cases the installation is dedicated to thispurpose.

Active privacy screening is normally achieved using multiple conespeakers or flat panels often dedicated to this purpose.

Passive sound insulation is commonly used in buildings to reduce thetransmission of sound from one room or area to another.

Perimeters anti intruder devices are usually positioned on windows anddoors and detect movement or vibration if disturbed.

Anti vandalism systems normally include video cameras, infrared lightingand intruder devices designed to detect movement.

Counter espionage issues are significant where relevant and would be thesubject of additional passive security systems, i.e. window shutters orscreens.

In some countries, Sweden for example, CCTV monitoring of individuals isnot permitted unless it is known that the individuals are committing anoffence or breaking the law.

As can be seen in many buildings the fragmentation of the systems designoften results in a multiplicity of audio and screening systems, cameras,and detection devices often resulting in excessive costs and wastedresources.

New legislation relating to noise and its control in building standardsin the US (HIPPA privacy standard) and in Europe introduce demands thatcombine some or all of the various functionality described above intoone installation classification, offering an opportunity to create a newapproach to satisfy the varying needs of architects and specifiers andconstruction contracting companies.

This is also relevant to the control of noise in highly populated noisyenvironments such as call centres or night clubs where being able tomake phone calls requires privacy and privacy, as well as masking toensure that the recipient on the other end of the line can hear what youare saying.

Additionally, new European disability legislation relating toinformation communication, particularly to people with impaired visualsense, imposes new standards on those providing information anddirection in public places. It is understood that this new legislationwill challenge local authorities, exhibition organisers and public spaceorganisers to create a new approach to provide an audio output to thoseprovided for in the legislation.

It can be seen that the approach of converting surfaces and structuresthat were not originally designed to transmit audio signals into audioemitting surfaces or structures emitting positive audio (voice musicetc) or masking or screening signals can have many advantages from acommercial, legislative or installation point of view, as well as fromthe end user's or customer's point of view.

In the use of loudspeakers or panel acoustic emitters to provideinformation in public spaces it is usual that the sound emitted from thepanel or loudspeaker is at a constant volume, or may be turned up anddown manually in response to complaints or requests. This isinconvenient and results usually from variations in the ambient noiselevel so that the emitted sound will at different times appear eithertoo loud or not loud enough. If a loudspeaker is used as the emitter thepoint source nature of this emitter means that the sound is oftenprojected beyond the area in which it is required and creates a noisenuisance.

It is well known that automatic gain control (AGC) circuits have beenused in cars to increase the volume from the radio as the car goesfaster and the ambient noise level increases. It is also known thatsignal compression has been used to reduce the dynamic range of radiooutput in car radios so that the quiet pieces of music can still beheard above high ambient noise levels, without making the louder piecesIn the music too loud. Both of these mechanisms are designed to avoidthe driver having to constantly adjust the volume controls. It has beenfound that point source emitters, loudspeakers, cannot usefully becontrolled in this way unless used in a tightly defined volume of space(for example a set of headphones). It is well known that that soundneeds to only be a small number of decibels higher than the ambientnoise level to be noticed (at the lower end of the range) and to beheard and understood (at the upper end of the range).

Our PCT application PCT/GB02/01 111 describes an application for the useof actuators, and more particularly magnetostrictive actuators, to drivepanels to be used as advertising or information media, for examplekiosks in shops, the shop window itself, or train and bus panels andwindows.

SUMMARY OF THE INVENTION

This invention relates to a system solution in which the surfaces,panels and structural elements that make up buildings and vehicles, anda multiplicity of products used in day to day life such as signs,tables, bars, walls, dividers, screens desks, cupboards and cabinets,can be acoustically activated by either single or multiple actuatorsattached to the panels themselves or the structure that supports thepanels, either by direct stimulation using an audio signal, or bycreating an audio signal in response to a sensing system, therebycreating a smart surface to achieve any number of levels offunctionality, but not necessarily be limited to all, as describedherein.

According to the Invention, there is provided an audio system, forexample for use in enclosed spaces, comprising an audio frequencyactuator coupled to a panel, for example within or defining saidenclosed space, so as to cause the panel to radiate sound when an audiosignal is supplied to the actuator by a controller, and an acousticsensor coupled to said panel or to an adjacent panel so as to senseacoustic vibrations in said panel, the sensor being connected to thecontroller, whereby the controller is arranged to change the audiosignal supplied to the actuator according to the vibrations sensed bythe sensor.

Another aspect of the invention provides an audio system, comprising anaudio frequency actuator coupled to a panel so as to cause the panel toradiate sound when an audio signal is supplied to the actuator by acontroller, and an acoustic sensor coupled to said panel or to anadjacent panel so as to sense acoustic vibrations in said panel, thesensor being connected to the controller, whereby the controller isarranged to detect predetermined characteristics of the sensed acousticvibrations and to output an alerting signal in response thereto. Thisoutput may be acoustic, or may trigger a remote device, for example aCCTV camera or a remote alarm.

Yet another aspect of the invention relates to apparatus which providesan audio signal that has an a perceived reducing effect on the ambientnoise in the vicinity, whereby it is perceived that the ambient noise islower or less persuasive due to the proximity of the mask source to theuser. This effect may be a psycho-acoustic effect due to the way thatthe brain perceives the mask as the dominant signal, so reducing theapparent ambient noise.

A further aspect of the invention provides a method of and apparatus foraffecting noise levels in a controlled manner to enable the user toperform a task in an improved manner despite high levels of ambientnoise. In one embodiment this might be in a club or bar or restaurantwhere a large surface emitter is used to create an audio signal thatscreens the ambient noise allowing conversation, phone calls to be madeor simply a lower level of ambient noise to be experienced away form thegeneral noise.

The audio frequency actuator can be integrated into the panel'sconstruction, either internally or externally, or it could beretrospectively fitted to an existing panel.

Preferably this will include audio reproduction, public announcement,supplementary emergency announcement, multi-media, and presentationamplification. The invention may also address internal noise management,personal privacy screens, room privacy screens, external noise control,as well as possibly external counter espionage security and intruder andvandalism detection sensing.

The audio output that is seen when an actuator is coupled to a rigidpanel transmits audio to both sides of the panel. The effect isapproximately equal on both sides. This can be adjusted by the use ofacoustic insulation whereby one side of the panel is acousticallyinsulated from the other by means of a soft infill material such asfoam, rubber silicone or similar or a baffle or reflective materials toensure the signal is predominantly in one direction. In some instanceshowever the use of a two way communication is of value, for example ontrain windows where the audio within the carriage and on the platformwould be a benefit. Similarly when a sensing system is incorporated thismay be sensing on one side and acting on the other side of a panel (forexample in a room in a hotel to reduce the effect of noise betweenrooms. Similarly in a double glazed unit the actuator may be on theinner of the front pane and sensing movement or pressure on the outerpane of glass.

Another application of this technology could be in the conversion of astructure to enable it to be able to communicate an audio signal as wellas a visual image, for example a map or timetable. Increasing demand onthe part of the regulators to provide for visually impaired people hasincreased the requirement to provide sound from a growing number ofinformation sources normally not associated with sound generation.Traditional methods of audio reproduction will create noise pollutiondue to their directional characteristics and will be limited by thenoise pollution that they create. The integration of an acousticallyactive surface or structure would allow the manufacturer of the smartsurface or structure to comply with these new regulations withoutincreasing noise pollution. In this invention the panel is driven as aconsequence of the relationship to the driven frame, enabling the visualimagery to be changed at will with no need for any modification to theaudio generating arrangement. The acoustic dynamics of the driven planarsurface tends to show a multiplicity of small point sources that behaveas one flat panel of source sound creating a lower level of sound over awider area of audio throw.

Where others have claimed the accuracy of positioning of the actuator iscritical to the performance of the panel, the massive power output ofthe magnetostrictive enables the actuator to be discreetly positionedwithin the structural element or any other suitable place that does notaffect the users view (if disposable, or transparent), the visual designand character or other functionality that the sign or structure mighthave.

The system that provides the functionality of audio signage or audiostructures in its simplest form is a signal generator that provides anaudio signal to the visual panel or structure.

It can be appreciated that more complex systems, including sensingcapability for noise management, and other levels of functionality canbe built into this system which when combined with a digital signalprocessing system will allow any specific signage or signage structureto be both monitored and addressed externally or locally if the userchose to interrogate using an integrated touch panel or sensing system.In this way an attack, an enquiry (contact) or a specific noise reducingsignal can be sent to the identified sign or sign structure by theprocessor.

If this approach was taken within say a national transport systemsignage structure any sign within the system fitted with a two waysensing system could be used as a communicator to any other sign in thesystem similarly fitted as a form of intercom or communication system.National updates could also be provided across this medium.

As each device may be fitted with its own signal amplifier, or providedfor from the centralised processor, an ability to interrogate at anypoint in the system could be limited to audio reproduction within theimmediate locus of the sign or structure, or transmitted throughout thefull network.

This would have the advantage of allowing centralised digital audio tobe stored for distribution throughout the whole network or on a localbase only.

The audio performance of this smart surface does not rely on modifyingor adding devices to the graphic material, which shall be used to conveythe visual imagery only. This visual imagery may be replaceable ordisposable for convenience of repeated use. According to the invention,there is provided a structure of rigid members that features an audiosystem that converts the otherwise non-audio designed product orstructure (for example an information sign or a bus shelter or anelement thereof) for use in public and commercial spaces, comprising anaudio signal generator or radio link to a similar device and either asingle or a multiplicity of audio frequency actuators coupled a part ofthe structure so as to cause the structure and the panel to radiatesound when an audio signal is supplied to the actuator by a controller.In some manifestations of the device an audio sensor is coupled to thesign or structure so as to sense audio frequency vibrations in theimmediate vicinity, the sensor being connected to the controller,whereby the controller is arranged to change the audio signal suppliedto the actuator according to the vibrations sensed by the sensor.

According to the invention, there is provided an acoustic devicepossibly but not limited to a magnetostrictive actuator acousticallycoupled to a structural member or members providing multiplefunctionality including some but not necessarily all and not limited to,the provision of local public announcements, external publicannouncements, public timetable information, promotional messages,reproduction of music for entertainment purposes, and emergencyannouncements, as well as active sound masking of extraneous noise fromthe other side of the structure within the locus of the structure.Additionally anti attack, or vandalism detection may be included as afunction of the actuator as it can also be tuned to intelligently senseactivity on its outer face, either by reacting to sound pressure, orphysical pressure (physical vandalism, or attack) or by recognising theeffect of a tool or pen if scratched or written on.

The construction of the structure and the surfaces therein can vary, thecommon features being at least one large panel of rigid (at least in oneaxis) glass, plastic, wood or other sheet material of transparent,translucent or opaque finish, and a support structure of aluminium,stainless steel, painted steel, MDF glass, plastic, sheet GRC, GRP, woodor wood panelling or any other material used in the traditional signageand advertising or bus shelter market.

The smart surface or structure can be used in public, public access orcommercial places where the addition of an audio signal can beadvantageous for the purposes of information, advertisement or promotionby the use of high-force, wide-band acoustic actuators to create anaudio signal using any number of elements of the structure of the signfor the purposes of generating a local audio signal. The input to theactuator can be any means of audio signal generator, CD, Mini disc, PC,media server or MP3, or a radio linked device that converts the signalfrom any type of remote signal generator. This invention can bedescribed as a single driven element of structure with it's associatedacoustic locus properties or a driven assembly of elements thereof whena multiplicity of elements are activated. The driven structure has beendesigned to accept the removable visual panel ensuring that the outputforce of the magnetostrictive drive will be sufficient to communicate avibration through the often larger expanse of the visual panel creatinga fuller audio locus around the entire structure.

The smart surface could contain printed information that shows a floorplan of an area as well as printed information intended to allow theuser to locate a specific zone within the area. An overlay touch panelusing some form of inductive, capacitive or other sensing device couldbe used to allow the use to touch a specific area of the sign in orderto prompt an audible sound-bite of information. If used in conjunctionwith a local authority information service or timetable, instructionsand information can be communicated aurally to the user.

As a system solution it is anticipated that smart surfaces andstructures will have advantages In many areas of public and commercialspaces where changeable public information or aural messages for thevisually disabled are required by the impending legislation, or where adeeper level of information is required to enforce or support thesignage information. Where an intermittent reactive audio output isrequired, for example as someone approaches the sign or structure, asimple infrared or PIR detector can be integrated into the assembly thatrecognises the persons approach and triggers the audio message.

Where an external update of information is required to be transmittedaudibly to someone in the vicinity of the smart surface or structure acombination of transmission and detection can be used to ensure that theaudio signal is not transmitting to an empty space and the system can beforced to only communicate when required by someone being in theimmediate detectable vicinity.

Pressure from advertisers on media companies also indicates a desire toexpand the two-dimensional medium of printed advertising to encompassaudible messages and information, and the massive expansion of the useof digital signage if not controlled can create a cacophony of noise inthe environment that is not desirable or acceptable.

Another application for smart surfaces would be to control noise inpublic places such as bars and restaurants where the high level ofbackground noise from neighbouring conversations to background music tothe noise associated with food and drink serving, can make it difficultto hold a private conversation, or indeed any conversation at all forthose with less acute hearing. Similarly it can be seen that the presentinvention provides a system for local generation and control of noise byusing the magnetostrictive actuators attached to drive table tops, bars,large panels of flat rigid material mounted under or into the ceiling orfloor, wall panels or other selected areas or structures that are notnormally associated with audio output to create an improved noisecontrol system. This system may be used in for example a club or barwhere noise control is required to permit phone calls to be made eventhough the caller is in close proximity to the noise source. In thisscenario a panel of material could be used to transmit a masking signalthat would oppose the ambient noise. In the vicinity of the planarmasking signal it would be easier to converse due to the psycho-acousticeffect of the more constant white or pink masking signal, and also itwould be possible to make a phone call without the phones microphonebeing affected by the masking signal. In this instance the generatedsignal would be designed not to conflict with the sensitive microphoneof the phone by using appropriate frequency signals.

Similarly in a call centre where there are a high density of operatorswho work in close proximity to each other (normally a six foot pitch)there is a need to mask some of the cacophony of noise generated by theoperators talking at the same time. By using the magnetostrictiveactuators to drive the desk or the walls (which by definition are nearthe caller) psycho-acoustically the operator will hear more of theconsistent sound of the mask and less of the background noise, and ifthe frequencies are controlled to not interfere with the telephonemicrophone the recipient will also benefit from the reduced level ofbackground noise perceived due to the addition of the mask.

As a system solution it is anticipated that this invention will haveadvantages in many areas of both domestic and commercial buildings,transportation of many types, and temporary and emergency structuresincluding more cost effective sound installations, discreet and easierto design into schemes with additional opportunities, be more costefficient, more reliable, addressable and future proofed to cater fornew emerging higher demand building, accommodation, information, privacystandards. The invention is equally applicable to the conversion ofstructures such as tables, signs, bars and any other assemblies ofelements of sufficient rigidity and Integrity to be converted to anaudio output by the addition of a magnetostrictive actuator as describedbelow.

According to another aspect of the invention, there is provided anacoustic device possibly but not limited to a magnetostrictive actuatoracoustically coupled to a panel providing multiple functionalityincluding some but not necessarily all and not limited to, thereproduction of music for entertainment purposes external publicannouncements, advertising purposes, local public announcements,external supplementary emergency announcements multi-media reproductionand presentation amplification active sound masking of extraneous noisefrom the other side of the panel privacy screening and room privacywithin the locus of the panel or structure or localised privacyscreening panels within. Additionally anti intruder, counter espionageor vandalism detection devices may be included as a function of thesystem's ability to monitor the condition of the panel.

The actuator also may be able to intelligently sense activity on itsouter face, either by reacting to sound pressure or physical pressure(wind noise, physical vandalism, or attack) or by recognising the effectof a tool or pen if scratched or written on.

A counter espionage aspect of the system is described and claimed in ourco-pending International Patent Application PCT/GB02/01111.

Detection of external pressure, sound pressure or physical pressure willpreferably be via a sensor integrated into the actuator or via a remotesensor, which may be attached to the body. This sensor can either beintegrated into the magnetostrictive actuator as a secondary function ofthe Terfenol-D material (or other GMM) or a piezoelectric device in theline of excitation, above or below the active core. It may measureactual force or it may measure the reaction force. The function of thissensor is either to sense that actual output signal or to sense in orderto instruct the active device.

In a particular type of graffiti a hardened tool or similar is used todamage the surface of the glass by scratching. This has a severe visualeffect on the glass and is commonly referred to as Dutch Graffiti.Another form of graffiti is with marker pens and aerosol spray paint. Ineach case a different acoustic signal will be detectable in the glass orsurface being sensed by an integrated or separately mounted sensor. Inthe case of the hardened tool, a distinct signature in the region of 250Hz to 12 KHz can be recognised and a signal sent to the controller.

In the case of anti graffiti sensing and external ambient noise sensing,this can be determined in a number of ways. Either the encoder interfacebox will be set up to look for one or more of the types of signals Itexpects (either by determining a preset sequence or selection offrequencies or another means), for example marker pen or hardened tool,or it could alternatively be set to look for the trend associated withan arising external noise such as airplane or traffic noise. It can beunderstood that any number of presets or learning algorithms could beused to seek and mask or screen or issue an antiphase signal tocompensate or reduce the effect of the sensed noise. This could includenoise from outside say a building site, noise from an adjoining room orspace, noise from a specific signal such as a tool or an attack orvandalism as described or simply to create a local ambient noise screenthat will mask conversation or discussion in one part of a room.

It will be understood that, while the surface or panel to be soundedmight conveniently have a generally rectangular shape, for example whenused as a window, the invention is not limited to the use of smartsurfaces having any particular shape or purpose.

The smart surface could be a wall, or a door, or a ceiling or a floor, avertical panel a horizontal panel, a table, an element of a largerstructure, or any member that exhibits sufficiently rigidcharacteristics that will support audio generation usingmagnetostrictive actuators. A number of smart surfaces could be attachedtogether to create a room or a volume of space general bounded by sides(for example a bus shelter). The room could be a single module as in atemporary building or self contained cabin, or it could be part of amultiplicity of rooms as in a building. The rooms could be zones withinlarger rooms and may not be fully contained by walls. The rooms may bestatic and anchored to the ground, or mobile and part of a transportsystem. The rooms may be subdivided with different functionalityprovided by alternate smart surfaces that use the same invention toprovide for the acoustic environment as described.

The construction of the smart surface can vary, the common featuresbeing rigidity (at least in one axis) and size, including, glass,plastic, metal, MDF, sheet GRC, GRP, plasterboard, dry-wall, woodpanelling or any other material used in the traditional building andtransport industry.

The smart surface can be of composite construction using different typesof material with cores and additional functionality skins, for exampleinsulation board for temporary building construction, featuringstructural Integrity outer skins, solar reflecting sheets, foam coresstructural honeycomb cores, aerospace aluminium honeycomb corescorrugated cores and extruded polycarbonate or similar structuralsheets, and fire insulation membranes as integral parts of its makeup.The mass of the panel can be low (small window panels) to massive 400+Kgplate glass or single skin ceiling sheets suspended or adhered to asuitable support structure.

The actuator is preferably a giant magnetostrictive material (GMM)actuator, for example of the type described and claimed in ourco-pending International Patent Application PCT/GB02/01111 or a scaledup version of the same. Preferably, the actuator is bonded discreetlywithin the structure, or into or onto the panel or retrospectivelyfitted, for example by adhesive or by physical retention system ofscrews and mounting brackets.

The audio signal generated by any aspect of the above invention can beeither a positive audio signal or an apparent negative audio signal thatcounters the effect of high degrees of ambient sound for a number ofdifferent purposes as explained.

Another application for the acoustic device of the invention is in themasking or perceived reduction of ambient noise. By combining with thedevice a sensor integrated into it or remotely mounted a distance fromit or an integrated or remote microphone or the type that focuses somedistance from its physical location and noise reduction or screeningcontroller which generates an anti-phase masking or screening signalsuch as a white or pink noise signal corresponding to the noise receivedby the microphone or sensor, the device can be employed to reduceperceived noise in a room, noise coming into a room, or just affectnoise in a part of a room. Similarly this will be applicable tostructures that are being converted to audio generators out-with theroom definition. The noise reduction may be configured to have abroad-spectrum effect or to reduce the amplitude of selected frequencybands. By configuring the layout for example, it can be arranged toactivate locally when required, either triggered by ambient noisedetection, or by being switched on. In this way, for example, atemporary quiet zone could be provided in an open-plan office or thelike, without the need for providing relatively high-mass walls aroundthe zone, but just by activating the ceiling, floor or adjoining wallpanels. Similarly, providing patient privacy, for example in a hospital,could be achieved by activating the smart surface over or under a bedwhen occupied. This would also have the advantage of providing quieterconditions for a patient without the need for a separate room.

Where an intermittent reactive smart surface is required, for examplewindow or double glazing unit that detects and reduces for exampleaircraft noise, or building site noise transmission into a building, itwill be preferable to integrate the sensor into the actuator and mountthe actuator on to the outer glass panel to facilitate more accuratesensing.

Increasing demand on the part of building regulators has also increasedthe requirement to provide sound insulation both from out-with andwithin temporary buildings. The current construction methods used arelimited in the amount of noise that they can insulate against resultingin these types of buildings not being suitable for human habitationunless more material (and weight and cost) is added. The integration ofan active smart surface sound screen to the external panel walls ofthese buildings would allow the manufacturer to comply with these newregulations without increasing the material content and weightsignificantly.

Active smart surfaces could be used in trains where external track noiseor tunnel noise needs to be reduced or masked.

Where others have claimed the accuracy of positioning of the actuator iscritical to the performance of the panel, the massive power output ofthe magnetostrictive enables the actuator to be discreetly positioned inthe corner of the smart surface or any other suitable place that doesnot affect the users view (if glass) or other functionality that thesmart surface might have.

The system that provides the functionality of smart surfaces in itssimplest form is a signal generator that provides an audio signal to thedevice within or on the panel. This will reside within the encoderinterface box.

It can be appreciated that more complex systems, including sensingcapability functionality can be built into this system which whencombined with a digital signal processing system will allow any specificsmart surface to be both monitored and addressed. In this way an alarmor a specific noise reducing signal can be sent to the identified smartsurface address by the processor. This could include activating externaldevices such as CCTV cameras or security.

It will be necessary to have a number of inputs and outputs on theencoder interface box. These are shown schematically hereinafter in FIG.5.

It is intended that the encoder Interface box is completely universaland able to accept Inputs from a wide range of devices includinganalogue and digital audio, microphone and sensors.

Equally it is intended that this device can be used to monitor andaffect the output on a multiplicity of devices including as describedbut not limited to magnetostrictive devices.

If this approach was taken within, say, an office building any windowfitted with a two way sensing system could be used as a communicator toany other window similarly fitted as a form of intercom or communicationsystem.

As each device may be fitted with its own signal amplifier, or providedfor from the centralised processor, an ability to input at any point inthe system could be limited to audio reproduction either within thebounded volume or a single panel locus, or transmitted throughout thefull installation.

This would have the advantage of allowing centralised digital audio tobe stored for distribution throughout the smart surfaces in the buildingor to locally addressed surfaces only.

According to another aspect of the invention, there is provided a noisecontrol system comprising a microphone associated with a rigid surface,control means connected to the microphone to detect ambient sound andarranged to generate a control signal in anti-phase to the detectedsound, and a transducer supplied with the control signal, the transducerbeing attached to the surface so as to cause the surface to radiatesound waves which reduce the amplitude of the ambient sound In a regionadjacent to the microphone.

Preferably, the transducer comprises a giant magnetostrictive material(GMM) element whose change in strain under the influence of an audiofrequency magnetic field induces sound waves into the surface.

The actuator may, for example, be an actuator of the type disclosed andclaimed in our co-pending International Application WO 01/72084,although other forms of actuator will also be usable.

It has been found that by making the surface, for example a table orbar-top, radiate the sound waves, the local sound energy at themicrophone is too low to cause audio feedback in the system, but theoverall energy radiated is sufficient to achieve a significantnoise-reduction effect. It will be appreciated that, since theanti-phase sound or masking signal radiated is based on the soundreceived by the microphone, the noise reduction effect is greatest nearto the microphone and diminishes as one moves away from the microphone.For best effect, a plurality of microphones and associated actuators maybe required.

The control means is preferably arranged to filter the sound received bythe microphone, for example to filter out from the sound reductionprocess a voice local to the microphone, thereby permitting normalconversation to be carried on in the region of the microphone whilereducing background noise.

The transducer is suitably attached to the underside of a table-top, butwhere this is not practical it may be attached to the upper surface oronto a rigid part of the structure. The microphone could be mountedabove the surface, or below the surface with a hole being providedthrough the surface to permit the noise signal to be received.

This invention also provides means for varying the emitted sound levelso that it is a constant level above ambient and for shaping the emittedsound envelope so that it stays within the area in which it is neededand avoids unnecessary noise pollution. It can also be used to create anenvelope or curtain of white or pink noise or music signal so thatprivate conversations are masked and cannot be overheard or zones whereexternal noise is damped to create ‘quiet’ areas or areas where there isa perception of quiet.

BRIEF DESCRIPTION OF THE DRAWINGS

In the drawings, which illustrate exemplary embodiments of theinvention:

FIG. 1 is a diagrammatic sectional view of a combined acoustic actuatorand sensor;

FIG. 2 is a similar view of an alternative configuration of actuator andsensor;

FIG. 3 is a diagrammatic sectional view through a double glazed windowpanel having installed therein a combined actuator and sensor accordingto yet another embodiment;

FIG. 4 is a similar view to that of FIG. 3, showing the actuator andsensor device installed in a wall cavity;

FIG. 5 is a block circuit diagram of a controller In accordance with theinvention;

FIG. 6 is a view of a table having the noise control system installedthereon;

FIG. 7 is a sectional view through the transducer of the system In FIG.1;

FIG. 8 is a front elevation of a sign display adapted for audio output;

FIG. 9 is a top plan view of the sign of FIG. 8; and

FIGS. 10 and 11 illustrate the actuator and contoured mounting bracketused in the audio sign shown in FIGS. 8 and 9.

DETAILED DESCRIPTION OF THE ILLUSTRATED EMBODIMENTS

Referring first to FIGS. 1 and 2, the actuator is essentially asdescribed in our co-pending International Patent ApplicationPCT/GB02/01111, having a housing 1 which serves also as a reaction massand which contains a core 2 consisting of an element of a giantmagnetostrictive material (“GMM”) surrounded by an electromagnetic coiland located between permanent magnets. The element is pre-stressed bysprings 3 and coupled to a pusher 4 which Is in turn connected to a foot5, which in use is pressed against a surface into which the acousticwave is to be transmitted. A piezoelectric sensing element 6 isincorporated into the actuator to sense acoustic signals in the surfaceto which the actuator is attached. In the example shown in FIG. 1, thesensing element 6 is provided on the external surface of the foot 5,while in the example shown in FIG. 2, the sensing element is locatedbetween the core 2 and the internal surface of the housing 1.

FIGS. 3 and 4 illustrate a different type of combined acoustic actuatorand sensing element, in different locations in use. The actuator/sensordevice 30 is of the type described in our application NoPCT/GB2003/005616 and has the core 31 extending between the main body 32of the actuator and a foot 33 pivotally mounted thereto with a springconnection holding the components 32 and 33 together and providing apre-stress to the GMM element within the core 31. In FIG. 3, theactuator 30 is mounted between the spaced glass panes 34 and 35 of asealed double-glazed window unit so as to act on one of the panes. Thepiezoelectric sensing element 36 is mounted between the foot 33 and thepane 35. In FIG. 4, the actuator 30 Is mounted on the inner face of aplasterboard wall or ceiling member 41 which can be conventionallymounted on battens 42 attached to a solid wall structure 43.Alternatively, the wall may be a studwork structure or any otherbuilding structure involving plasterboard or other boarding. Theactuator 30 in FIG. 4 may be the same as that in FIG. 3, or thepiezoelectric sensing element may be incorporated into the actuator, forexample between the core 31 and the main body 32.

FIG. 5 illustrates a typical configuration of controller for the systemof the invention. The controller includes a central processor 50provided with audio inputs 51 for music, announcements orcommunications, for example, together with sensor inputs 52 connected tothe sensing elements in the actuators coupled to the controller, forexample those illustrated in FIGS. 1 to 4. A mains power supply 53 isincluded. Battery backup may also be provided. An audio output 54 isprovided to a power amplifier 55. This may in turn be connected to anumber of actuators in the building or vehicle, for example, or aseparate feed and amplifier may be provided to individual actuators orto separate groups of actuators. A white noise generator 56 is connectedto the processor to provide a sound-masking output to the actuators orto selected actuators in response to detected noise or to preventespionage by monitoring vibrations in windows or other panels, forexample. A noise recognition module 57 compares acoustic signalsdetected by the sensors with a library of acoustic signatures torecognise a potentially damaging attack on a panel, for example bycutting or scratching, and outputs an alarm signal in response todetection of such a signal. The alarm signal can give rise to audiooutput to the panel concerned and/or to adjacent panels, and a messagecan also be transmitted to a remote monitoring location via acommunications interface 58 and communications link 59 (e.g.RS232/RS488/IEEE 488.2/Ethernet).

FIG. 6 illustrates a typical arrangement installed In a table top, butit will be appreciated that the system is not confined to use withtables, or indeed on horizontal surfaces. The table, for example in abar or restaurant, has a table-top 60 provided with a central aperture61 there through, in which is located a microphone 62 to convert theambient noise into electrical signals which are then fed to a controller63, mounted beneath the table-top, for example. The controller 63suitably comprises a central processing unit programmed to perform afiltering operation which filters out speech adjacent to the microphoneand then to shift the phase of the remaining signal such that, whenreradiated by the transducer and table-top, as hereinafter described, itclosely approximates to ambient sound, but is 180 degrees out of phasetherewith, thereby substantially cancelling the sound, at least In aregion close to the microphone. The effect of this will be that peoplesitting at the table will experience a reduction in the general ambientnoise when they lean inwards towards the table's centre where themicrophone is located, permitting conversation to be more easily heard.The output signal from the controller 63 is fed to a GMM transducer 64,described hereinafter in more detail with reference to FIG. 7, attachedto the underside of the table so as to couple the audio signal into thetable top, which then acts as a loudspeaker to radiate the sound.

Another application for the system might be installed at a servingcounter or bar top, so that the barman or food server can hear ordersspoken near to the microphone forming part of the system, without theneed for the customer to shout to overcome general background noise.

Referring now to FIG. 7, the GMM transducer comprises a casing 65, forexample of steel to provide a return magnetic path for the magnets, ashereinafter described, in which is located a rod 66 of giantmagnetostrictive material (which for convenience may comprise two piecesof the GMM, end-to-end), with a non-magnetic spacer 67, for example ofaluminium or a ceramic material capable of transmitting force, disposedat each end thereof to space the GMM rod 66 from a pair of disc magnets68 of substantially greater diameter than the width of the rod. Aplastics core 69 serves to locate and hold the GMM rod 66 and spacers,and carries an electromagnetic winding 70 which is connected via wires(not shown) to a separate energising signal source. A foot 71 transmitsthe force produced by the actuator to the desired location.

It will be understood that the invention is not limited to the use of aparticular configuration of transducer, that illustrated in FIG. 7 beingshown merely as an example of a usable device.

While the system is illustrated with reference to horizontal surfaces,It will be appreciated that the sound radiating surface could bevertical, for example a wall panel. It is not essential for the surfaceto be planar.

FIG. 8 shows a typical audio sign construction featuring themagnetostrictive actuator 72 mounted inside a hollow structural post 73.The audio frequency generator 74 is also mounted within the hollow post73 along with the power supply and AGC control equipment where required.The hollow post 73 is excited by the actuator and a frequencytransmitted to the rigid visual panel 75 which is attached to the post.

FIG. 9 shows the magnetostrictive actuator 72 and the method ofattachment to the inside of the hollow post 73 by means of a contouredmounting bracket ensuring all generated signals are transmitted throughthe signs structure.

FIG. 10 and FIG. 11 show a detail illustration of the magnetostrictiveactuator 72 and contoured bracket 76.

1. An audio system, comprising an audio frequency actuator coupled to abody so as to cause the body to radiate sound when an audio signal issupplied to the actuator by a controller, and an acoustic sensor coupledto said body or to an adjacent body so as to sense acoustic vibrationsin said body, the sensor being connected to the controller, whereby thecontroller is arranged to change the audio signal supplied to theactuator according to the vibrations sensed by the sensor.
 2. An audiosystem, comprising an audio frequency actuator coupled to a body so asto cause the body to radiate sound when an audio signal is supplied tothe actuator by a controller, and an acoustic sensor coupled to saidbody or to an adjacent body so as to sense acoustic vibrations in saidbody, the sensor being connected to the controller, whereby thecontroller is arranged to detect predetermined characteristics of thesensed acoustic vibrations and to output an alerting signal in responsethereto.
 3. An audio system according to claim 1, wherein the actuatorand the sensor are coupled to the same body.
 4. An audio systemaccording to claim 3, wherein the sensor is incorporated into theactuator.
 5. An audio system according to claim 1, wherein the actuatoris a magnetostrictive actuator.
 6. An audio system according to claim 1,wherein the sensor is a piezoelectric device.
 7. An audio systemaccording to claim 1, wherein the body is rigid or flexible panel.
 8. Anaudio system according to claim 7, wherein the panel is a ceiling panel,a wall panel, a floor panel or a window pane of a building or vehicle.9. An audio system according to claim 1, wherein the controller isarranged to detect acoustic signals with predetermined characteristicsin the output from the sensor and to supply to the actuator an audiooutput signal selected according to said characteristics.
 10. An audiosystem according to claim 9, wherein the detected characteristicsrepresent ambient noise and the output signal is a random sound signalsuch as white noise or pink noise adapted to provide a degree of maskingof the ambient noise.
 11. An audio system according to claim 9, whereinthe detected characteristics represent the quality of the audio signalsupplied to the actuator and the controller is adapted to correct thesupplied audio signal in accordance with the detected characteristics toimprove the sound radiated in the space.
 12. An audio system accordingto claim 2, wherein the predetermined characteristics represent adamaging attack on said body.
 13. An audio system according to claim 2,wherein the predetermined characteristics represent the sounds generatedby a person within the space.
 14. An audio system according to claim 2,wherein the alerting signal causes output of an audible and/or visiblealarm.
 15. An audio system according to claim 13, wherein the alertingsignal is used to control the operation of lighting and/or heatingwithin the space.
 16. An audio system according to claim 13, wherein thealerting signal is used to control the supply of audio signals to theactuator.
 17. A noise control system comprising a microphone associatedwith a rigid surface, control means connected to the microphone todetect ambient sound and arranged to generate a control signal inanti-phase to the detected sound, and a transducer supplied with thecontrol signal, the transducer being attached to the surface so as tocause the surface to radiate sound waves which reduce the amplitude ofthe ambient sound in a region adjacent to the microphone.
 18. A noisecontrol system according to claim 17, wherein the transducer comprises agiant magnetostrictive material (GMM) element whose change in strainunder the influence of an audio frequency magnetic field induces soundwaves into the surface.
 19. A noise control system according to claim17, comprising means for filtering from the control signal speechadjacent to the microphone.
 20. The noise control system according toclaim 17, installed in or on a bar or counter.
 21. The noise controlsystem according to claim 17, installed in or on a bar or counter. 22.An audio system, comprising an audio frequency actuator coupled to abody which is not a flat panel so as to cause the body to radiate soundwhen an audio signal is supplied to the actuator by a controller.
 23. Anaudio system according to claim 22, wherein the body is a tubular body.24. An audio system according to claim 23, wherein the tubular body isan item of street furniture or a support therefor.
 25. An audio systemaccording to claim 24, wherein the tubular body is a supporting post fora sign.
 26. An audio system according to claim 23, wherein the tubularbody is non-circular in section.
 27. An audio system according to claim23, wherein the audio frequency actuator is mounted within the tubularbody.
 28. An audio system according to claim 23, wherein the audiofrequency actuator is a transducer comprising a giant magnetostrictivematerial (GMM) element whose change in strain under the influence of anaudio frequency magnetic field induces sound waves into the surface. 29.An audio system according to claim 2, wherein the actuator and thesensor are coupled to the same body.
 30. An audio system according toclaim 29, wherein the sensor is incorporated into the actuator.
 31. Anaudio system according to claim 2, wherein the actuator is amagnetostrictive actuator.
 32. An audio system according to claim 2,wherein the sensor is a piezoelectric device.
 33. An audio systemaccording to claim 2, wherein the body is rigid or flexible panel. 34.An audio system according to claim 33, wherein the panel is a ceilingpanel, a wall panel, a floor panel or a window pane of a building orvehicle.